Modeling event-based temporal variability of flow resistance coefficient

During the storm duration, the effects of surface resistance on the developing and receding overland flow depths (h(j)) on different flow parameters like the overland flow resistance coefficient (N-j), flow velocities (v(j)), Reynolds number (R-j), and Froude number (F-j) have been studied for the six natural catchments (0.012-92.5 km(2)) located in different agroclimatic regions of India. The kinematic wave (KW) equations are used for simulation of overland and channel flows using explicit methods for developing numerical solutions for the estimation of flow parameters at short durations. For the complete storm duration h(j)-N-j relationships have been found to form hysteresis loops. To predict resistance coefficients, simple h(j) - N-j relationships have been worked out separately for the rising and depleting overland flow conditions. Computed hydrographs simulated by incorporating these equations in the KW model agree well with the observed ones. The overall applicability of the suggested approach is successfully demonstrated under ungauged situations as well.